1. Field of the Invention
The present invention relates to a superconducting oxide material, and specifically a process for manufacturing a superconducting oxide ceramic material film, wherein crystals are uniformly aligned in a direction perpendicular or parallel to a surface portion on which the thin film is formed.
2. Description of the Related Art
Recently, superconducting ceramic materials have been attracting a great deal of attention. These materials were first reported by IBM's Zurich Laboratories in the form of Ba-La-Cu-O (BALACUO) type high temperature superconducting oxide material. In addition, the YBCO (YBa.sub.2 CuO.sub.6-8) types are also known. However, these types could be prepared only by mixing and firing various types of oxide powders to form tablets, so that even when a Tc onset of 90 K. was obtained, a sufficiently thin film was not possible. In addition, it was completely unknown that the thin film formed at a lower temperature can have crystal grains uniformly oriented in a direction with reference to the surface portion on which the film is formed (which is hereinafter referred to as the film-forming surface portion).
The critical current density of these superconducting materials with polycrystalline oxide structure in tablets is small. In order to correct this problem, it is desired that all the ab surfaces of the crystal grains (also referred to as the C surface, the surface perpendicular to the c axis direction) be mutually oriented.
Furthermore, it is strongly desired that the Tco (temperature at which resistance is zero) of the superconducting oxide material be higher. It is desirable that operation be possible at the temperature of liquid nitrogen (77 K.) or a higher temperature, and that, in turn, the Tco temperature of 90 K. or higher be available in the structure of the thin film.
In addition, there is no means of performing oxygen treatment at lower temperature that will reach into the interior without damaging the surface; also, in the case of a porous superconducting material, even if annealing is possible there has not been any means of performing, in a short time, oxide annealing of single crystals or a closely similar material which have been adequately oriented.